Kant’s self-styled “Copernican revolution” was a turning inward, to the study of the mind, for solutions to the perennial problems of philosophy. Kant is, among other things, something of a reactionary. Writing at the end of the century of the Enlightenment he sought to defend Christianity, freedom and morality from the threat posed, as he saw it, by empiricism’s atheistic, amoral worldview. Particularly Kant tried to devise an antidote to Hume, and realized that Hume’s Lilliputian psychology, with its denial that anything like the “mind” could even be said to exist beyond the “impressions” caused by sensory experience, was a weak spot in the empiricist argument. Developing an ambitious account of the way the mind organized the “sensory manifold” with a conceptual framework of its own (including the “concepts” of space, time, cause and effect, multiplicity etc), Kant contained the world as understood by the new natural science within a mental representation: the “phenomenal” world was the world as represented by the rational mind, not to be confused with the actual, “noumenal” world.
Kant’s revolution has practically defined philosophy, certainly popular philosophy, ever since. From the German-language transcendental idealists, psychoanalysts, phenomenologists and critical theorists to the French-language existentialists, structuralists and deconstructionists to the English-language phenomenalists, language philosophers and, yes, cognitive scientists, it is hard to find any major philosophical movement of the last two hundred years that does not reflect the influence of Kant. He is one of the few canonical philosophers, whose influence can be seen in the views of the general public, including a great many people who have never heard of him or who do not appreciate that their own views are substantially Kantian. His message that our own minds broadly condition “how we see things” is congenial to a modern world of great cultural, ethnic and political diversity (notwithstanding the fact that Kant himself thought that the rational mind, qua rational, was the same for all).
Although Kant was engaged in a close struggle with Enlightenment empiricism his revolution was not a turning back of the clock. He presented an alternative not only to the empiricists but to the classical metaphysical tradition as well. The eclipse of explicitly metaphysical philosophy for much of the 20th century is of course due to some extent to the cultural impact of modern science, but it also reflects Kant’s core argument that psychological epistemology is first philosophy. What license have we, stuck as we are inside our heads, to make metaphysical speculations about “the external world”?
As a consequence of this it is now difficult for us to appreciate Plato, that most metaphysical of philosophers. So deeply and widely internalized is Kant’s thesis - that the conceptual order of the world is a projection from the mind onto the world - that many people simply cannot hear Plato anymore. In fact many people, even some philosophy professors and certainly a great many students, simply believe that Plato is Kant: the Platonic universals are Kant’s categories. What else could they be, when it is taken as axiomatic that the mind constructs a representation of the world? A smart student, in a typical but relatively explicit exchange, insisted that there was no such thing as the property of circularity or, for that matter, the set of circular concrete particulars: our minds create such categories out of whole cloth, apparently: and this was the view that he ascribed to Plato (he thought that he knew nothing of Kant). He was not at all impressed when I pointed to the two identical circular ceiling fans. Similarity itself, he understood, was a projection of the mind, a feature of the mental representation. As for the textual evidence (which in reality is clear and systematic), Plato is gnostic, all riddles; no one can really understand him. After all, he can’t mean what he is manifestly saying. Attempts to disabuse people of these notions, when not rejected out of hand, are met with bewilderment, anger, and various stages of grief and disillusionment. The slightly more sophisticated perceive that Plato is a bad, bad influence, putting us all at risk of totalitarian dystopia with his irresponsible foundationalism. One of my students told me that her law professor informed the class that he would have voted for Socrates’ execution.
Ah, well. Forgive this old classroom veteran my hobby-horses. Suffice it to say that, for good or ill, Plato is not Kant. Plato is making assertions about the ontology of the universe (of being); just what Kant and his followers claim cannot be done. Listening to what Plato has to say will help us to develop a resolution of the problem of rationality, at least insofar as this problem is one of the mind-body problems. I am not here trying to determine exactly what Plato the individual man actually believed in its fine points. I am not an historian of philosophy. My interest in Plato is the same as my interest in Hilary Putnam or John Searle or Jerry Fodor or for that matter the person sitting next to me on an airplane: if they have interesting ideas that inspire me in my own thinking I am grateful for the acquaintance. The reader whose principal interest is in contemporary philosophy of mind can rest assured that that is my principal interest as well, and that I am not wandering off into exegesis for its own sake. It’s just that I sincerely believe that Plato is the best exemplar of the best argument for resolving the problem of rationality.